Worksheet

Part One - Background information

Copy the information below into your background section on your worksheet.Today you will observe another protist. In the previous labs (online or in class) you observed a type or protist called a protozoan. Now you will observe a type of protist called an algae. All algae are plant-like protists. This is because they are autotrophs---they use photosynthesis to make their own food.

The algae you will observe today is called a euglena. It is a type of euglenoid. Euglena are examples of algae because its cell contains chloroplasts which allow it to carry out photosynthesis. However, scientists have observed that euglena can also be heterotrophs; they can also eat to obtain energy!

Euglena also have adaptations that help them survive. For example, they have flagella that allow them to move, a pellicle which gives them their shape, and an eye spot which is used to help detect the location of light. In fact, if you place euglena in a container, place it by a sunny window, and cover half the container, the euglena will move to the sunny side!

Part Two - Cell Structures

Copy the information below to your worksheet.The structure of the euglena is similar to the other protists we have studied. On the outside of the euglena is the pellicle. Recall that the pellicle is a stiff but flexible covering that gives the organism its shape. Underneath the pellicle you will find the cell membrane. You will also find the flagellum, the long whip-like structure used for movement.

Inside the euglena we will find several familiar organelles. First, you should be able to observe the nucleus. Unlike the paramecium, the euglena only has one nucleus. It controls the cell’s functions. In addition you should be able to observe contractile vacuoles. Recall that the contractile vacuole collects and expels excess water from the cell. Another common organelle is the chloroplast. These green structures allow the euglena to carry out photosynthesis.

Now let’s learn about some new organelles. First, you should be able to observe a red spot. This is called the eye spot (also known as the stigma). It helps the euglena detect sources of light. It works by blocking some light sources so the euglena can tell which direction the brightest source is coming from. Second, you will notice long, rod-shaped parts. These are called the paramylon granules. They are similar to food vacuoles. They store sugar created during photosynthesis. Sometimes these appear as spots on or near the chloroplasts.
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Before moving on, watch the videos to see how many parts you can identify.

Video 1How many parts can you identify below? Try to find the chloroplasts, paramylon granules, contractile vacuoles, and the eye spot (stigma).

Video 2Observe the flagella. How many does the euglena have? Observe how the pellicle allows the organism to bend, but keep, its shape.

Part Three - Labeling the Diagram

Part Four - Reflecting

Answer the following questions.1. Which group of protists to euglena belong to?2. Euglena contain chloroplasts. When light is limited, they can eat particles to obtain energy. Are these organisms classified as heterotrophs or autotrophs?3. Euglena are not the only organisms that have flagellum. Zooflagellates are protozoa that also have flagella. Although euglena and zooflagellates move by flagella, why are these organisms classified differently?4. Name two organelles you could find in a euglena that you couldn't find in a zooflagellate.5. You place millions of euglena into a container and place it by the window. The entire container is a bright green color as the euglena swim freely. You cover half the container, block out the sunlight. At the end of the day, you return to the container and find that all the euglena are now on the uncovered side. Explalin why this happened. Your answer must include the works: eye spot (stigma), sunlight, and photosynthesis.

Copyright 2010-2019 Peter Ower. Some images and content provided by other authors and is cited as such.